Prevention of Thaumasite Sulfate Attack in Binders Containing Interground Limestone




<正>With the increased levels of interground limestone being used in certain types of cements, as well as the use of limestone filers in concrete placed in sulfate exposures,there is concern with an increased risk for thaumasite sulfate attack(TSA),especially in cooler climates.To address this,in 2010 the Canadian CSA A3000 standard adopted a cold temperature mortar bar sulfate expansion test limit(similar to ASTM C1012 but with exposure at 5℃).It was found that non-sulfate resistant Portland-limestone cement bars did deteriorate due to TSA,but that this damage could be mitigated when used with sufficient levels of slag,Class F fly ash,metakaolin or ternary mixtures with silica fume, similar to the approach often used to prevent normal temperature sulfate attack.This presentation will show the mortar bar data along with performance of concrete prisms also stored in 5℃and cyclic temperature exposure to sulfate solutions. Originality The standard test method developed is the first for evaluating the potential for thaumasite sulfate attack(TSA).In addition,it has been demonstrated that types and levels supplementary cementing materials used to mitigate conventional sulfate attack are similar to those needed to mitigate TSA.Confirmatory work with concrete has shown that the standard test is overly severe,due to the detrimental effect of early exposure to cold temperature on hydration of slowly reacting po zzolans.


Sulfate attack;;thaumasite;;limestone;;supplementary cementing material


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